Horn for loudspeaker



Feb. 3, 1959 c. Q. GLASSEY HORN FOR LOUDSPEAKER Filed March 12, 1958INVENTOR. COURTNEY Q. GLASSEY BY 5 Z Z blis AGE/YT United States PatentHORN FOR LOUDSPEAKER Courtney Q. Glassey, Rochester, N. Y.

Original application May 2, 1955, Serial No. 505,367,

now Patent No. 2,835,335, dated May 20, 1958. Digizdgiggmd thisapplication March 12, 1958, Serial No.

7 Claims. (Cl. 181-31) The present invention relates tosound-reproducing apparatus and more particularly to a multiple hornstructure within a housing or cabinet in which two horns substantiallyencircle the speaker for increasing the speaker efliciency as well asthe frequency response of the speaker and is a division of my co-pendingapplication, Serial No. 505,367, filed May 2, 1955, and now U. S. PatentNo. 2,835,335

Inexpensive speaker cabinets have used cone speakers and cabinets of theopen back and closed back, or bass reflex types, and such systems varyfrom poor to fair in bass response and from low to moderate in expensein the order designated. The efficiency of the speaker in such cabinetsvaries from 3 percent to 10 percent.

While the advantages of the flared, folded horn are known to thoseskilled in the art, the difficulties encountered in designing such hornshave resulted in many disadvantages. All of the designs utilizecomplicated and expensive cabinetry to form the folded horn sections andwith many such horns there is a waste of cabinet space. Also, there istoo high an acoustic capacitance which results in the loss of higherfrequencies due to many foldings, or to 180 folding where the dimensionsare unfavorable. There is also a loss of eificiency and a waste of spacedue to the use of a chamber or cavity enclosing the speaker to absorbthe back wave. The design of horns known in the art is such that thecabinet must be placed either against the wall of a room, or adjacent aroom corner, whereby the effective mouth area 'of the horn will beincreased. When such horns have been compromised by being given a largermouth and a shorter length, the bass deficiency cannot be compensatedfor by the use of simple bass booster circuits.

In the present invention, the above disadvantages and shortcomings ofthe known structures are overcome. By improving the coupling of thevibrating diaphragm of the speaker through a large mouth to theatmosphere, the horn efficiency is increased to 40 percent anduniformity over the whole frequency range is improved. The reduced conetravel resulting from the use of a horn reduces distortion, improvestransientresponse, increases definition and reduces cost by permittingsmallermagnet structures to be used in the speakers. For full efficiencydown to the cut-off frequency, the mouth area and the horn length shouldbe in balance and compatible with the housing or cabinet dimensions.This can be accomplished by providing a relatively long, flared hornwhich v has a flare in at least one plane and which couples a chamberwithin the housing to the atmosphere, said chamber enclosing one side ofthe speaker diaphragm. Such a horn substantially encircles the speakerand provides, in effect, a close approximation of an exponential hornwhich directs the lower frequencies of the speakerto an 7 open side, ofthe housing. The back of the speaker being horn-loaded gives good andextended bass. With the horn structure described hereinafter, radiationof the higher frequencies of the speaker is directed to the atmosphereby means of a short, flared horn which is partially encircled by thelong horn, the open side of the housing or cabinet providing a mouth foreach horn in accordance with the frequency range of each horn and beingdivided into a desired ratio of mouth sizes or areas by a partitionwhich also forms a common portion of the flare for both the long and theshort horns.

The frequency of the mechanical cross-over between the two horns iscontrolled by the design capacitance of the chamber and the long hornwhich directs the lower frequencies to the open side and by the designedbass cutoff frequency of the short horn which directs the higherfrequencies to the open side. The loud speaker is loaded to an optimumby the use of the dual horns, one horn being arranged with respect toeach side of the speaker diaphragm. The dimensions of the horn willdepend on its use and the bass response that is required. A small hornof less than one cubic foot of volume can be used for paging and publicaddress systems where bass response is unimportant. However, horns oflarger volume are required in high fidelity systems wherein good bassrespouse is required and necessary. The horn structure described in moredetail hereinafter can be readily incorporated within a cabinet thatcontains a sound source such as a radio receiver, television receiverand/or record-playing equipment of either the disc or tape type.

The dual horn arrangement also possesses several inherent advantageswhich are not found in single horn compression systems. It is well knownthat a single horn is restricted in the range of frequencies which canbe covered and can only give optimum performance over a range of threeor four octaves. On the other hand, a dual horn system in which thehorns are calculated to complement each other, a range of six to eightoctaves can be attained. Also, in a dual horn system the speakerdiaphragm is not susceptible to rupturing by a steep pressure wave frontdeveloped outside of the cabinet or housing in which the speaker ismounted, because such pressure is applied by the dual horns to bothsides of the speaker diaphragm and not to only one side as in the caseof a single horn system.

The primary object of the invention is, therefore, to provide asound-reproducing apparatus in which separate horns are utilized fordirecting the lower and higher frequencies of a speaker to the same openside of the structure housing the speaker, both horns having-a flare inone plane and the horns substantially encircling the speaker and beingconcentric thereabout.

Another object of the invention is to provide a soundreproducingapparatus in which the lower frequencies of the speaker are directed tothe atmosphere by a relatively long, flared horn which couples anopening in a chamber within the housing enclosing one side of thespeaker diaphragm to an open side of the housing and which substantiallyencircles the speaker, and the higher frequencies of the speaker aredirected to the atmosphere by a short, flared horn which couples anopening in the chamber on the other side of the speaker diaphragm to thesame open side with one side thereof common to and forming a portion ofone flared side of the long horn.

A still further object of the invention is to provide a simplifieddesign for a dual horn sound-reproducing apparatus which, by varying thesize of the apparatus, can be readily adapted to paging, public addressand high fidelity 3 skilled in the art by the description of theinvention which follows. Reference is now made to the accompanyingdrawing in which like reference numerais designate like partsthroughout, and wherein:

Fig. 1 is a perspective view with one side of the housing or cabinetremoved and showing a structure of sheet metal by means of which thespeaker is enclosed and by which 'two horns are formed with the mouthsthereof contiguously arranged with respect to the same open side;

Fig. 2 is a perspective view similar to Fig; 1 in which the speakerenclosure and the horns are fabricated-of a formable non-metallicmaterial; and V Fig. 3 is a perspective viewof a wall-type speaker inwhich the housing is given a shape other than rectangular,

the horns being formed in a manner similar to that shown in Figs 1 and2.

In the embodiment of the invention disclosed in Figs.

l and 2, a cabinet 19 is shown with a diaphragm-type loud speaker Siltarranged within the cabinet. Cabinet is substantailly rectangular andcomprises the two larger and opposed sides -12 and 13 and the threesmaller sides 14, 15' and 16, enclosing the opposed sides and having anopen side 17. Open side 17 permits communication between the interior ofcabinet 10 and the atmosphere. If desired, an opening can be provided inone of sides 12 .or 13 to permit direct radiation to the atmosphere froma supplementary treble speaker mounted within cabinet 10. In theembodiment disclosed in Fig. 1, speaker 80 is enclosed by a structure 83which can be formed of sheet metal and arranged between opposed sides 12and 13. Structure '83 is formed so as to provide a chamber 85 aboutspeaker '80 and is provided with an opening 84 which permitscommunication of the lower frequencies from the one side of the speakerbetween chamber 85 and the interior of cabinet 19, the chamber beingformed about speaker 80 by walls 86, 87 and 88 together with opposedsides 12 and 13. Speaker 30 is mounted on wall 88 and aligned withopening 90 which permit the higher frequencies from the other side ofthe speaker diaphragm to be communicated to the atmosphere.

From opening 84, walls 86, $7 and 88 are formed so .as to provide arelatively long, flared horn 82 together with the interior surfaces ofsides 16, 15 and 14 respectively, the flare being in a plane parallel tothat of opposed sides 12 and 13 and increasing from opening 84 to openside 17 in only one dimension.

In. order to direct the higher frequencies of speaker 8t) to theopenside, a partition 91 is arranged'between sides 12 and 13 to provide ashort, flared horn 81 connecting opening $5 to open side 17. Horn 81,therefore, comprises a portion of wall 88, partition 91 and opposedsides 12 and 13, the partition 91 being common to both horns 81 and 82and dividing the open side 17 into two contiguous horn mouths in apredetermined ratio of areas depending on the cross-over frequencydesired from the speaker. frequencies from the front side of the speakerto the atmosphere via opening 90 and open side 17, whereas the lowerfrequencies from the rear side of speaker 80 are communicated to theatmosphere via opening 84 and horn 82 to open side 17. While the higherfrequency Horn 81 permits communication of the higher p horn 81 is shortas compared with the lower frequency ft will shift along wall 38 or 37,depending on the rota-' tion of speaker .819 and partition 91 will beextended and still form a wall common to each horn. Although the innerlength of born 82 (walls 85, 87, and partition 91) much shorter than theouter length (sides 15, 16

and 14), this can be partially equalized by covering the 'Walls andpartition with'a good insulator and by using sound diffractors to retardthe wave front shorter path.

The structure disclosed in Fig. 2 is similar to that of Fig. 1, exceptthat walls 86 and 8'7 andpartition A are shown as comprising a singlesheet which can be formed or molded from plywood, 'Fiberglas, metal or aplastic material. Such a structure can provide a smooth and continuoushorn surface together with low installation cost.

In the foregoing embodiments, the cabinet 16 has been described andshown as a rectangular cabinet suitable for receiving the signal outputfrom a radio, television receiver, record player, or as part of acabinet suitable for housing any' combination of these soundreproducers. However, as will be readily apparent to those skilled inthe art, the cabinet may be varied in shape depending on the size of thespeaker and its application. For example, the dual, concentric hornarrangement described hereinabove can very well be utilized for publicaddress systems in which the housingor cabinet can be of a form shown inFig. 3. Accordingly, the reference herein to housing or cabinet can beused interchangeably whether of a rectangular form as shown in Figs. 1and 2 or of a type having a bell-shaped mouth and molded of a plastic,

along the Fiberglas, or similarly suited material, as shown in Fig. 3.

The embodiment shown in Fig. 3 comprises a housing 70 molded of plasticor Fiberglas and of two parts which are joinedto form a complete unit.Opening 84 and 90 are provided, as in the above-described embodiments,and the interior surface of the curved wall 71 together with the outersurface of partition 91 and the curved interior surface of the housingforms the long, flared horn 82, the short flared horn 81 being formed bya portion of the housing and the other surface of partition 91. As inthe embodiments described above, speaker is mounted within the chamber72 with horn 82 permitting the lower frequencies to be communicated viaopening 84 to the open end and the atmosphere and horn 81 permitting thehigher frequencies to be communicated viaportion of sides 75 and 76beyond the flare are actually parallel to the median plane. Also, it maybe desired to flare horns 8 1 and 82 in two dimensions so that sides 75and 76 will not be parallel with respect to the median plane but will besymmetrical thereto. The arrangement and shape of the sides of housing70 will not, however,

alter the relationship of horns 31 and 82.

Since many modifications of the invention will be apparent to thoseskilled in the art, the invention is not to be limited to the disclosedembodiments but is defined by the appended claims.

Having now particularly describedmy invention, what I desire to secureby Letters Patent of the United States and what I claim is: a

1. Asound-reproducing apparatus comprising in combination,-a hollowhousing having an aperture for establishing communication betweentheinterior of said housing and theatmosphere, at least onevibrating-diaphragm type loud speaker arranged within said housing, achamber within said housing enclosing said speaker and having a firstopening for establishment communication between the rear side of thespeaker diaphragm and-the interior of said housing and a second openingfor establishing communication between the front side of the.speakendiapbragmand the interior of said housing, .a:part'itionarranged' within said housing, said partition dividingsaid"aperture'into two contiguous horn mouths of a predetermined ratio ofareas,.a first horn substantially encircling said chamber and having aflare increasing in at least one dimension from said first opening tosaid aperture for directing the lower frequencies of said speaker fromsaid first opening to one of the horn mouths, and a second horn having aflare increasing in at least the same one dimension as said first hornfrom said second opening to said aperture for directing the higherfrequency of said speaker from said second opening to the other of thehorn mouths, a portion of said first horn being arranged about saidsecond horn with said partition forming a portion common to each of saidhorns. I

2. A sound-reproducing apparatus comprising in combination, a hollowhousing having an aperture for establishing communication between theinterior of said housing and the atmosphere, at least onevibrating-diaphragm type loud speaker arranged within said housing, achamber within said housing enclosing said speaker and having a'firstopening for establishing communication between the rear side of thespeaker diaphragm and the interior of said housing and a second openingfor establishing communication between the front side of the speakerdiaphragm and the interior of said housing, a partition arranged withinsaid housing and extending from said second opening to said aperture,said partition dividing said aperture into two contiguous horn mouths ofa predetermined ratio of areas, a first horn substantially encirclingsaid chamber and having a flare increasing in at least one dimensionfrom said first opening to said aperture for directing the lowerfrequencies of said speaker from said first opening to the larger of thehorn mouths, and a second horn having a flare increasing in at least thesame one dimension as said first horn from said second opening to saidaperture for directing the higher frequency of said speaker from saidsecond opening to the smaller of the horn mouths, a portion of saidfirst horn being arranged about said second horn with said partitionforming a portion common to each of said horns.

3. A sound-reproducing apparatus comprising in com bination, a hollowhousing having at least two sides substantially symmetrical to a medianplane and an open side normal to said median plane, at least onevibratingdiaphragm type loud speaker arranged within said housing, achamber within said housing enclosing said speaker and having a firstopening for establishing communication between the rear side of thespeaker diaphragm and the interior of said housing and a second openingfor establishing communication between the front side of the speakerdiaphragm and the interior of said housing, a partition arranged withinsaid housing and extending from said second opening to said open side,said partition dividing said open side into two contiguous horn mouthsof a predetermined ratio of areas, a first horn formed by the interiorsurface of said housing, a portion of the exterior surface of saidchamber and said partition, substantially encircling said speaker andhaving a flare increasing in at least said median plane from said firstopening to one of the horn months for directing the lower frequencies ofthe speaker from said first opening to the open side, and a second hornformed by a portion of the exterior surface of said chamber and saidpartition, arranged within said first horn and having a flare increasingin said same median plane as said first horn from said second opening tothe other of the horn months for directing the higher frequencies ofsaid speaker from said second opening to said open side.

4. A sound-reproducing apparatus comprising in combination, a hollowhousing having at least two substantially parallel sides and an openside normal to said parallel sides, at least one vibrating-diaphragmtype loud speaker arranged within said housing, a chamber within saidhousing enclosing said speaker and having a first opening forestablishing communication between the rear side of the speakerdiaphragm and the interior of said housing and asecond opening forestablishing communication between the front side of thespeakerdiaphragm and the interior of said housing, a partition arranged withinsaid housing and extending from said second opening to said open side,said partition dividing said open side into two contiguous horn mouthsof a predetermined ratio of areas, a first horn formed by the interiorsurface of said housing and said parallel sides, a portion of theexterior surface of said chamber and said partition, substantiallyencircling said speaker and having a flare increasing in one dimensionfrom said first opening to the larger of the horn months for directingthe lower frequencies of the speaker from said first opening to the openside, and a second horn formed by a portion of the exterior surface ofsaid chamber and said partition, arranged within said first horn andhaving a flare increasing in the same one dimension as said first hornfrom said second opening to the smaller of the horn mouths for directingthe higher frequencies of said speaker from said second opening to saidopen side.

5. A sound-reproducing apparatus comprising in combination, asubstantially rectangular cabinet having two opposed and substantiallyparallel sides and four sides enclosing said two opposed sides to formsaid cabinet, one of said four sides being open for establishingcommunication between the interior of said cabinet and the atmosphere,at least one vibrating-diaphragm type loud speaker arranged within saidcabinet, a chamber enclosing said speaker and having a first opening forestablishing communication between the rear side of the speakerdiaphragm and the interior of said cabinet and a second opening forestablishing communication between the front side of the speakerdiaphragm and the interior of said cabinet, a first horn substantiallyencircling said chamber and having a flare in a plane substantiallyparallel to the plane of the opposed sides for directing the lowerfrequencies of said speaker from said first opening to the open side,and a second horn having a flare in the same plane as said first hornfor directing the higher frequencies of the speaker from said secondopening to the open side, said second horn being shorter than said firsthorn and having one flared side thereof in common with a portion of oneflared side of said first horn and dividing the open side into two hornmouths of a predetermined ratio of areas.

6. A sound-reproducing apparatus comprising in combination, asubstantially rectangular cabinet having six sides, two of the opposedsides being larger than the four sides enclosing said two opposed sidesto form said cabinet and one of said four sides being open forestablishing communication between the interior of said cabinet and theatmosphere, at least one vibrating-diapln'agm type loud speaker arrangedwithin said cabinet, a chamber enclosing said speaker and having a firstopening for establishing communication between the rear side of thespeaker diaphragm and the interior of said cabinet and a second openingfor establishing communication between the front side of the speakerdiaphragm and the interior of said cabinet, a partition arranged betweensaid opposed sides and extending from said second opening to the openside, said partition dividing the open side into two areas of apredetermined ratio, a first horn substantially encircling said chamberand having a flare in a plane parallel to said opposed sides fordirecting the lower frequencies of said speaker from said first openingto the open side, and a second horn having a flare in the same plane assaid first horn for directing the higher frequencies of the speaker fromsaid second opening to the open side, the flare of said first horn beingdefined by the exterior surface of said chamber, one side of saidpartition and the inner surface of the three sides of said cabinet andthe flare of said second horn being defined by a portion of the exteriorsurface of said chamber and the other side of said partition.

7. A sound-reproducing apparatus comprising in combination, arectangular cabinet having six sides, two of the opposed sides beinglarger than thefour sides enclosing said two opposed sides to form saidcabinet and one of said four sides being open for establishingcommunication between the interior of said cabinet and the atmosphere,at least one vibrating-diaphragm type loud speaker arranged within saidcabinet, a chamber enclosing said speaker and having a first opening forestablishing communication between the rear side of the speakerdiaphragm and the interior of said cabinet and a'second opening forestablishing communication between the front side of the speakerdiaphragm and the interior of said cabinet, a first horn substantiallyencircling said chamber and having a flare increasing in one dimensionand toward the open side for directing the lower frequencies of saidspeaker from said first opening to the open side, and a second hornhaving a flare increasing in the same one dimension'as said first hornand toward the open side for directing the higher frequencies from saidsecond opening to the open side, said second horn being shorter thansaid first horn and having one flared side thereof common to a portionof one flared side of said first horn'and dividing the open side intotwo contiguous horn mouths of a predetermined ratio of areas.

No references cited.

